Comparisons of Fifth-, Sixth-, and Seventh-Generation Continuous Glucose Monitoring Systems

BACKGROUND

Between-system differences for continuous glucose monitoring (CGM) devices have important clinical consequences.

PURPOSE

Here we review attributes of Dexcom's fifth-, sixth-, and seventh-generation (G5, G6, and G7) CGM systems.

METHODS

Accuracy metrics were derived from preapproval trials of the three systems and compared after propensity score adjustments were used to balance baseline demographic characteristics. Metrics included mean absolute relative differences (MARD) between CGM and YSI values and the proportion of CGM values within 20% or 20 mg/dL of the YSI values ("%20/20"). Ease-of-use was evaluated by formal task analysis.

CONCLUSIONS

Adjusted MARD and %20/20 agreement rates were 9.0%/93.1% (abdomen-placed G5), 9.9%/92.3% (abdomen-placed G6), 9.1%/93.2% (abdomen-placed G7), and 8.2%/95.3% (arm-placed G7). Task analysis favored G7 over earlier systems. Favorable clinical outcomes such as hemoglobin A1c reduction and hypoglycemia avoidance seen with G5 and G6 are anticipated with G7 use.

Testing the Real-World Accuracy of the Dexcom G6 Pro CGM During the Insulin-Only Bionic Pancreas Pivotal Trial

Continuous glucose monitors (CGMs) have transformed the way people with type 1 diabetes can self-monitor glucose levels. Past studies have evaluated the accuracy of CGMs in clinic-based studies, but few have analyzed their accuracy in real-world settings. The Insulin-Only Bionic Pancreas Trial provided the opportunity to assess real-world accuracy of the blinded Dexcom G6 Pro sensor over the first 48-60 h of wear using a blood glucose meter (BGM) as a comparator for 1073 CGM-BGM pairs across 53 participants. The mean absolute relative difference (MARD) was 11.0% over a median period of 50 h (range 47-79 h). The MARD was 13.6% in the first 12 h, 10.5% in hours 12-24, and 10.1% after the first 24 h. These results are comparable with accuracy shown previously with laboratory-based measurements and provide real-world evidence of Dexcom G6 Pro accuracy, which improved after the first 12 h and then remained stable thereafter. Clinical Trial Registry: clinicaltrials.gov; NCT04200313.

Health Care Professionals' Perspectives on Use of Diabetes Technologies for Managing Visually Impaired Patients With Diabetes

BACKGROUND

Despite well-established safety and efficacy of diabetes technologies in management of diabetes, their utility in visually impaired patients is currently unknown. We aimed to identify providers' preferences and challenges to prescribing diabetes technologies for visually impaired patients.

METHODS

A survey-based study among health care providers in the United States seeing visually impaired patients with diabetes and using diabetes technologies was conducted. The quantitative and qualitative responses were analyzed using Student t test and χ2 tests.

RESULTS

Of 79 providers, 66 completed the survey and were included in the analysis. Insulin pens and hybrid closed-loop systems were preferred insulin delivery systems for managing visually impaired patients with diabetes. Despite 96% of the providers recommending continuous glucose monitoring (CGM) for their visually impaired patients with diabetes, only 55% were aware of the voice-activation feature of Dexcom G6. Voice activation to announce glucose values and audible glucose alerts were two major incentives for selecting CGM. System initialization was seen as a prevalent challenge of using CGM in visually impaired patients with diabetes. Providers who are using CGM for visually impaired patients reported benefits for patients using the voice-activation feature for six months included HbA1c reductions of >0.5% (by 87% of providers) and less hypoglycemia (by 45% of providers).

CONCLUSIONS

The CGM is the preferred glucose monitoring method for managing visually impaired patients with diabetes. Providers face many challenges of initiating CGM in these high-risk patients. Voice-activation feature of G6 CGM is underutilized and providers who used the system reported positive outcomes in visually impaired patients.

Accuracy of a Seventh-Generation Continuous Glucose Monitoring System in Children and Adolescents With Type 1 Diabetes

BACKGROUND

Accuracy of a seventh-generation "G7" continuous glucose monitoring (CGM) system was evaluated in children and adolescents with type 1 diabetes (T1D).

METHODS

Sensors were worn on the upper arm and abdomen. The CGM data were available from 127 of 132 participants, ages 7 to 17 years, across 10.5 days of use, various glucose concentration ranges, and various rates of glucose change for comparisons with temporally matched venous blood glucose measurements (YSI). Data were also available from 28 of 32 participants, ages 2 to 6 years, for whom capillary (fingerstick) blood provided comparator glucose values. Accuracy metrics included the mean absolute relative difference (MARD) between CGM and comparator glucose pairs, the proportion of CGM values within 15 mg/dL or 15% of comparator values <100 or ≥100 mg/dL, respectively, and the analogous %20/20 and %30/30 agreement rates.

RESULTS

For participants aged 7 to 17, a total of 15 437 matched pairs were obtained from 122 arm-placed and 118 abdomen-placed sensors. For arm-placed sensors, the overall MARD was 8.1% and overall %15/15, %20/20, and %30/30 agreement rates were 88.8%, 95.3%, and 98.7%, respectively. For abdomen-placed sensors, the overall MARD was 9.0% and overall %15/15, %20/20, and %30/30 agreement rates were 86.0%, 92.9%, and 97.7%, respectively. Good accuracy was maintained across wear days, glucose ranges, and rates of glucose change. Among those aged 2 to 6, a total of 343 matched pairs provided an overall MARD of 9.3% and an overall %20/20 agreement rate of 91.5%.

CONCLUSIONS

The G7 CGM placed on the arm or abdomen was accurate in children and adolescents with T1D. NCT#: NCT04794478.

Real-time continuous glucose monitoring improves glycemic control and reduces hypoglycemia: Real-world data

AIM

To study the effect of real time continuous glucose monitor (RT-CGM) use on glycemic parameters in patients with diabetes mellitus (DM) in real world practice.

METHODS

We retrospectively studied 91 adult subjects with DM who had been using Dexcom™ RT-CGM. Two consecutive hemoglobin A1c (HbA1c), both prior to and after at least 3 months of RT-CGM initiation, were collected. A total of 31 subjects completed a 5-14 day user blinded CGM using a Freestyle Libre™ prior to RT-CGM initiation. The first two week period following at least 3 months use of RT-CGM was analyzed for CGM metrics.

RESULTS

A total of 51.6 % of subjects had T1DM, 34.1 % used continuous subcutaneous insulin infusion (CSII), and 62.6 % had DM for > 10 years. Both HbA1c obtained following RT-CGM initiation decreased significantly compared to baseline (8.11 + 1.47% vs 7.69 + 1.25 %; P = 0.002 & 8.16 + 1.51 % vs 7.62 + 1.06 %; P = 0.001). Subjects with baseline HbA1c > 7.0 % showed even more robust reduction in both HbA1c after RT-CGM initiation (8.74 + 1.24 % vs 7.99 + 1.22 %; P = 0.000 & 8.74 + 1.32 % vs 7.85 + 1.07 %; P = 0.001). On comparison of CGM metrics, there was a significant reduction in time spent in hypoglycemia (sugars < 70 mg/dl) including severe hypoglycemia (sugars < 54 mg/dl) after initiation of the RT-CGM (9.16 + 8.68 % vs 1.29 + 2.21 %; P = <0.001 & 4.58 + 5.43 % vs 0.28 + 0.58 %; P = <0.001). CoV of glucose was also decreased significantly (39.61 + 9.36 % vs 31.06 + 6.74 %; P = <0.001) with RT- CGM use.

CONCLUSION

RT-CGM use for at least 3 months in patients with DM results in meaningful HbA1c reductions with stable glycemic control without increasing the risk of hypoglycemia.

Accuracy and Safety of Dexcom G7 Continuous Glucose Monitoring in Adults with Diabetes

Background: We evaluated the accuracy and safety of a seventh generation (G7) Dexcom continuous glucose monitor (CGM) during 10.5 days of use in adults with diabetes. Methods: Adults with either type 1 or type 2 diabetes (on intensive insulin therapy or not) participated at 12 investigational sites in the United States. In-clinic visits were conducted on days 1 or 2, 4 or 7, and on the second half of day 10 or the first half of day 11 for frequent comparisons with comparator blood glucose measurements obtained with the YSI 2300 Stat Plus glucose analyzer. Participants wore sensors concurrently on the upper arm and abdomen. Accuracy evaluation included the proportion of CGM values within 15% of comparator glucose levels >100 mg/dL or within 15 mg/dL of comparator levels ≤100 mg/dL (%15/15), along with the %20/20 and %30/30 agreement rates. The mean absolute relative difference (MARD) between temporally matched CGM and comparator values was also calculated. Results: Data from 316 participants (619 sensors, 77,774 matched pairs) were analyzed. For arm- and abdomen-placed sensors, overall MARDs were 8.2% and 9.1%, respectively. Overall %15/15, %20/20, and %30/30 agreement rates were 89.6%, 95.3%, and 98.8% for arm-placed sensors and were 85.5%, 93.2%, and 98.1% for abdomen-placed sensors. Across days of wear, glucose concentration ranges, and rates of change, %20/20 agreement rates varied by no more than 9% from the overall %20/20. No serious adverse events were reported. Conclusions: The G7 CGM provides accurate glucose readings with single-digit MARD with arm or abdomen placement in adults with diabetes. Clinicaltrials.gov: NCT04794478.

Contact allergy to the Dexcom G6 glucose monitoring system -role of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate in the new adhesive

BACKGROUND

Skin reactions to the glucose monitoring systems Dexcom G5 and G6 have been rare. In 2019, the components of the adhesive were exchanged for better skin fixation. Since then, more and more patients experienced severe skin reactions. A few months ago, 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate (MBPA) was identified as a new component in the adhesive of the G6 model. Furthermore, it was suspected that isobornylacrylate (IBOA) was also a component of the exchanged adhesive.

OBJECTIVES

Our objective was to investigate if MBPA plays a major role in the increasing skin problems of patients without a history of IBOA-sensitization. Furthermore, our aim was to examine whether IBOA is contained in the newer model adhesive and may also contribute to allergic contact dermatitis (ACD).

PATIENTS AND METHODS

Five patients with a newly occurred ACD caused by the glucose monitoring system Dexcom G6 were investigated. Patch testing including MBPA in 3 different concentrations, as well as IBOA were performed. Gas chromatography-mass spectrometry of the newer system Dexcom G6 was carried out.

RESULTS

All patients were shown to be sensitized to MBPA, while MBPA 0,5% showed the strongest reaction. On the other hand, IBOA was tested negative.

CONCLUSION

In our study group MBPA was observed to be the triggering allergen of the recently changed adhesive.

Comparison of Cgmanalysis, a Free Open-Source Continuous Glucose Monitoring Data Management and Analysis Software, with Commercially Available CGM Platforms: Data Standardization for Diabetes Technology Research

Background: Cgmanalysis is an open-source software based on the R programming language for data management and descriptive analysis of data from continuous glucose monitoring (CGM). We sought to validate the summary measures calculated by cgmanalysis against the results from proprietary software associated with four CGM commercially available models. Methods: Two weeks of data from 188 patients with type 1 diabetes using commercially available CGMs. Freestyle Libre Gen 1 (n = 53), Medtronic Guardian 3 (n = 52), Dexcom G6 reported by Dexcom Clarity (n = 48), and Dexcom G6 reported by Tandem (n = 35) were analyzed using proprietary software and cgmanalysis. Agreement was assessed using scatterplots, Bland-Altman plots, and equivalence tests. Results: Good agreement was obtained for all glycemic summary measures for all CGMs assessed. None of the differences between the cgmanalysis package and the manufacturers' software were outside the prespecified bounds of equivalence. Conclusions: Cgmanalysis is a validated open-source software to analyze commercially available CGM data and can be used to standardize diabetes technology research.

Real-World Evidence and Glycemic Improvement Using Dexcom G6 Features

Background: Optional features of continuous glucose monitoring (CGM) systems empower patients and caregivers to understand and manage diabetes in new ways. We examined associations between use of optional features, demographics, and glycemic outcomes. Methods: Retrospective cohort studies were performed with data from US-based users of the G6 CGM System (Dexcom, Inc.). For all cohorts, data included sensor glucose values (SGVs). In separate cohorts, use of alert features (for hyperglycemia, existing hypoglycemia, and impending hypoglycemia), remote data sharing feature (Share), software for retrospective pattern analysis (CLARITY), "virtual assistant" feature that announces the current SGV and trend in response to a spoken request were assessed. Descriptive statistics were used to summarize feature set utilization patterns and relate them to glycemic outcomes. Results: Most individual features were consistently adopted by high proportions of G6 users. Threshold SGVs chosen for activating hyperglycemia and hypoglycemia alerts varied with age and were higher among the youngest and oldest patients. Use of the Share feature was more common among young patients and those with type 1 diabetes. Individuals who used more of the alert and notification features had more favorable glycemic outcomes, including time in range (TIR), than those who used fewer. More extensive engagement with CLARITY notifications was associated with higher TIR. Frequent use of the virtual assistant feature was associated with higher TIR and lower mean SGV. Conclusions: Optional features of the G6 CGM system are acceptable to and appear to benefit patients who use them. Different levels of engagement suggest that demographics and personal circumstances play a role in how patients and caregivers use CGM features to help manage diabetes.

Accuracy of FreeStyle Libre in Adults with Type 1 Diabetes: The Effect of Sensor Age

Background: FreeStyle Libre is a factory-calibrated continuous 14-day glucose sensor. Little is known about the accuracy of FreeStyle Libre as a function of sensor age. Methods: We assessed the accuracy of FreeStyle Libre in 14 adults with type 1 diabetes. Each study participant attended our research facility for two or three 24-h visits, during which they wore a FreeStyle Libre aged 0-1 day, 5-7 days, or 13-14 days. Plasma glucose levels were measured every 10-30 min using YSI2300 STAT Plus Analyser. Participants also wore Dexcom G5^® glucose sensor aged 1-2 days. We assessed sensors' accuracy using mean absolute relative difference (MARD) between FreeStyle Libre, the Dexcom G5 sensor, and plasma glucose. Results: We had 1930 pairs of FreeStyle Libre sensor-plasma glucose measurements, collected from 36 FreeStyle Libre sensors, 18 of which were sensors aged 0-1 day, 9 were sensors aged 5-7 days, and 9 were sensors aged 13-14 days. The mean and median MARD for FreeStyle Libre sensors aged 0-1 days were 14.5% and 11.2%, respectively, and for sensors aged 13-14 days were 14.7% and 11.2%, respectively, but for sensors aged 5-7 days were 7.8% and 6.6%, respectively (P = 0.03 vs. sensors aged 0-1 days, and P = 0.06 vs. sensors aged 13-14 days). The percentage of points falling in the potentially dangerous zones C, D, or E in Clarke's error grid analysis were 1.9% for FreeStyle Libre sensors aged 0-1 day, 0.2% for sensors aged 5-7 days, and 0.4% for sensors aged 13-14 days. The overall accuracy of FreeStyle Libre and Dexcom G5 sensor was the same (mean MARD 12.8% and 12.5%, respectively; P = 0.57). Conclusions: FreeStyle Libre's accuracy is adequate during its entire lifetime but is least accurate during its first and last days. ClinicalTrials.gov Identifier: NCT02814123.

A history of continuous glucose monitors (CGMs) in self-monitoring of diabetes mellitus

Self-monitoring of glucose for individuals afflicted with diabetes mellitus has allowed patients to take control of their disease and thus directly affect the outcomes related to it. It has been almost a century since the first test to monitor one's sugar was developed; that being a urine test. The most well-known and prominent medical device for monitor blood glucose for individuals with diabetes are the finger-prick devices. This itself is an approximately 50year old technology. More recently has been the introduction of continuous glucose monitors (CGMs) which entered the market place in the last year of the 20th century. As this technology has been further refined and improved, limitations associated with it have decreased. The scope of this review is to present a brief history of CGMs, both with the development of these medical devices and the challenges/limitations that they have shown.